A knife would be good. I can see something like this changing the weight of a blade entirely, and that would be an issue for combat.

[So Alucard turns, looking at the knives. Considering, before he picks up one that is surprisingly slender looking. There are larger ones, bigger blades, but Alucard seems to respond to it well. He gives the air an experimental stab, and then nods.

He offers it back to Viktor.]

This one would be a good test of balance and weight.